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A nutritionist claims that the mean tuna consumption by a person is 3.5 pounds per year. Asample of 80 people shows that the mean tuna consumption by a person is 3.2 pounds peryear. Assume the population standard deviation is 1.22 pounds. At a= 0.07, can you reject theclaim?Identify the null hypothesis and alternative hypothesis

Sagot :

Here is what we know:

Sample size: 80 people

Mean consumption by a person from the sample: 3.2 pounds

Sample standard deviation: 1.22 pounds

Tuna consumption according to the nutritionist claims: 3.5 pounds

Alpha: 0.07

First, we compute the standard deviation of the mean:

[tex]\sigma_{\mu}=\frac{\sigma}{\sqrt{n}}=\frac{1.22}{\sqrt{80}}\approx0.136\text{ pounds}[/tex]

Then, the z score for the nutritionist claims is given by:

[tex]Z=\frac{x-\mu}{\sigma_{\mu}}=\frac{3.5-3.2}{0.136}\approx2.2[/tex]

Then, according to a normal table, we have:

[tex]P(Z\ge2.2)+P(Z\leq2.2)=2\cdot(0.5-0.4861)=0.0278[/tex]

We can check that 0.0278 < 0.07, therefore the null hypothesis, is rejected.

The null hypothesis is given by:

[tex]\begin{gathered} P(z\leq Z_{null})+P(z\ge Z_{null})\ge1-0.07=0.93 \\ According\text{ to the normal table: }Z_{null}=\pm1.81 \\ =\frac{x_{null}-\mu}{\sigma_{\mu}} \\ \pm1.81=\frac{x_{null}-3.2}{0.136} \\ x_{null}=3.2\pm1.81\cdot0.136\approx3.2\pm0.25 \\ null\text{ hypothesis: 2.95}\leq x\text{ }\leq\text{ 3.45} \\ Alternative\text{ hypothesis: }x\leq2.95\text{ or }x\ge3.45 \end{gathered}[/tex]

Null hypothesis: 2.95 <= x <= 3.45

Alternative hypothesis: x <= 2.95 or x >= 3.45